WASHINGTON — The Justice Department is trying to protect its political appointees from the "Fast and Furious" scandal by concealing an internal "smoking gun" report and other documents that acknowledge the role top officials played in the program that allowed firearms to flow illegally into Mexico, according to the head of the Bureau of Alcohol, Tobacco and Firearms.

Kenneth Melson, ATF's acting director, also told congressional investigators in a private meeting over the Fourth of July holiday that the affidavits prepared to obtain wiretaps used in the ill-fated operation were inconsistent with Justice Department officials' public statements about the program.

Justice officials advised him not to raise his concerns with Congress about "institutional problems" with the scandal, Melson said.

"It was very frustrating to all of us," Melson told investigators, "and it appears thoroughly to us that the department is really trying to figure out a way to push the information away from their political appointees at the department."

Not only was the department slow to react, Melson said, but Justice officials indicated they did not want him to cooperate with Congress.

Justice Department officials denied they are stonewalling the congressional investigation. They said they are cooperating, and have been providing thousands of pages of documents and other material to the investigators.

The intent of Fast and Furious was to allow illegal straw purchasers to buy guns so ATF agents could follow the weapons and ferret out gun-smuggling routes into Mexico. But many of the approximately 1,700 weapons eluded tracing — some even before they were shipped over the border.

Nearly 200 of the weapons were later found at crime scenes in Mexico, and two were recovered at the scene of a U.S. Border Patrol agent's slaying in Arizona last December.